An in-vehicle wiring harness is exposed in a high-temperature environment during use. Further, waterproof performance is required for spliced portions of the wiring harness. A waterproofing agent is used for the spliced portions of the wiring harness exposed in such a high-temperature environment.
A resin composition as a water sealant (waterproofing agent) or the like is used to be reliably filled between twisted strands of a wire conductor and block leak paths among a plurality of wires of the wiring harness. For example, a method using a low-viscosity resin having a low contact angle, a method using a special means such as depressurization, pressurization or inclination, a method using an ultraviolet curable resin and the like are known to be applied for wire coatings and wire conductors (see, for example, patent literature 1).